Inlets of centrifugal compressors, blowers and pumps

ABSTRACT

This invention relates to improvements in the inlet of a centrifugal compressor. A stator comprising a row of slanted stationary blades is disposed in the air inlet of a centrifugal compressor, directing the fluid against the impeller blading in the general direction of rotation. A rotor is disposed in front of the stator, the rotor and stator forming a stage. The rotor produces velocity energy, and the stator reduces velocity energy with increase of pressure energy. The inlet conduit is forwardly enlarged - rearwardly reduced around the rotor-stator stage, to provide a large intake opening and to help precompress the fluid before it enters the impeller. Plural rotor-stator stages are disposed in the inlet conduit to increase pre-compression in the inlet. A peripheral aperture is provided in the inlet conduit around the first rotor, or the first rotor is projected from the lip of the inlet to increase the mass of intake and improve efficiency. The invention, at least in part, may also be applied to centrifugal blowers and centrifugal pumps.

Elite States atent Mittelstaedt [54] INLETS OF CENTRIFUGAL COMPRESSORS, BLOWERS AND PUMPS [72] Inventor: Georg S. Mittelstaedt, 274 73rd St.,

Brooklyn, N.Y. 11209 22 Filed: April 10, 1970 211 Appl. No.: 27,314

[52] US. Cl. ..4l5/62, 415/74, 415/122, 415/143 [51] Int. Cl ..F0ld 13/00 [58] Field of Search ..4l5/122,143,62, 183,215

[56] References Cited UNITED STATES PATENTS 2,069,640 2/1937 Beardsley, Jr. ..415/l83 2,074,184 3/1937 Kirgan ..4l5/183 2,166,276 7/1939 Anderson ..415/l83 3,447,740 6/1969 Fabri et a1. ..415/215 2,227,336 12/1940 Jamieson-Craig ..4l5/122 FOREIGN PATENTS OR APPLICATIONS 775,548 5/1957 Great Britain ..415/l43 931,344 2/1948 France ..4l5/143 973,616 2/1951 France ..4l5/l43 1,066,912 6/1954 France ..415/143 [4 1 Sept. 19, 1972 Primary ExaminerC. J. l-Iusar [57] ABSTRACT This invention relates to improvements in the inlet of a centrifugal compressor.

A stator comprising a row of slanted stationary blades is disposed in the air inlet of a centrifugal compressor, directing the fluid against the impeller blading in the general direction of rotation.

A rotor is disposed in front of the stator, the rotor and stator forming a stage. The rotor produces velocity energy, and the stator reduces velocity energy with increase of pressure energy.

The inlet conduit is forwardly enlarged rearwardly reduced around the rotor-stator stage, to provide a large intake opening and to help precompress the fluid before it enters the impeller.

Plural rotor-stator stages are disposed in the inlet conduit to increase pre-compression in the inlet.

A peripheral aperture is provided in the inlet conduit around the first rotor, or the first rotor is projected from the lip of the inlet to increase the mass of intake and improve efficiency.

The invention, at least in part, may also be applied to centrifugal blowers and centrifugal pumps.

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INLETS OF CENTRTFUGAL COWRESSORS, ELOWERS AND PUMPS This invention relates to improvements in the air inlet of a centrifugal compressor. It also relates to improvements in the inlets of centrifugal blowers and pumps.

In a centrifugal compressor, a rotating impeller with radial vanes is mounted on a shaft in a casing and is revolved at high speed. Air enters the impeller axially near the shaft and experiences an outward flow due to centrifugal action. As the fluid leaves the impeller at high speed, it is collected in a volute or a series of diffusing passages that reduce velocity energy with increase of pressure energy. The fluid is then discharged from the compressor.

The air inlet to the central part of the impeller may be just a central opening in the casing, or may be a passage or any form of conduit leading to the center of rotation. Often, there are central guide vanes mounted on the impeller or forming an integral part of the impeller and rotating therewith. There also may be separate rotating guide vanes.

All this is well known in conventional centrifugal compressors. It is also well known that a conventional centrifugal compressor has a relatively small intake opening and a limited mass of intake.

In the present invention, I improve the inlet of a centrifugal compressor. The improvements chiefly are: Stator blades in the inlet directing the fluid against the impeller or guide vane blading in the general direction of rotation; a rotor-stator stage in the inlet, the rotor producing velocity energy and the stator reducing velocity energy with increase of pressure energy; a forward enlargement rearward reduction of the inlet of the inlet to provide a large intake opening and to aid precompression in the inlet; plural rotor-stator stages in the inlet conduit to increase precompression.

Objects of this invention are to improve efficiency, to improve compression, to precompress the fluid in the inlet before it enters the impeller, to increase the capacity of centrifugal compressors, blowers and pumps in proportion to their sizes, to increase the mass of intake, to increase intake velocity.

These and other objects will become apparent in the description below, in which characters of reference refer to like-named parts in the drawing.

The drawing is schematic and is only meant to illustrate the principles of the invention. The invention is not limited to the particular examples illustrated, nor to the particular construction shown.

In the claims, by rotor is also meant rotating blades; by stator is also meant stationary blades; by rotorstator stage is also meant a rotor followed by a stator; by shaft is also meant spindle; by upstream of is also meant in advance of.

Referring briefly to the drawing,

FIG. ll shows a stator in the inlet of a centrifugal compressor.

FIG. 2 shows a rotor-stator stage in the inlet of a centrifugal compressor.

FIG. 3 is similar to FIG. 2, but a stator is disposed in front of the rotor.

FIG. 4 shows plural rotor-stator stages in the compressor-inlet.

FIG. 5 shows guide vanes forming part of the impeller, and a stator in front of the guide vanes.

FIG. 6 shows guide vanes forming part of the impeller, and a separate set of guide vanes in front.

FIG. 7, illustrates a single rotor forward of the impeller having a radial inlet to the rotor.

PKG. 8 illustrates a single rotor forward of the impeller having an axial inlet overlapping the rotor.

In the drawing, like parts are identified with the same numerals, as is feasible.

Referring in greater detail to the drawing, the centrifugal compressor of FIG. 1 has an impeller casing l of any suitable form and construction, and this houses an impeller 2. The impeller is carried on a shaft or spindle 3 which is rotated by any suitable means not shown. Outside the periphery of the impeller blade system is a volute 4, but any other diffusing means may be used. The numeral 5 indicates an air inlet to the central part of the impeller, and in the air inlet is provided a stator 6 comprising a row of slanted stationary blades. The stator is disposed axially in proximity to the central part of the impeller, and is disposed so that the entering fluid must pass through its blades before entering the impeller.

The stator blades are inclined so as to direct the inlet flow at a slant against the central part of the impeller in the general direction of rotation, thereby improving efficiency. The numeral '7 indicates a suitable slant of the stator blades, and 8 indicates the direction of impeller rotation.

It is to be noted that, with the stator, the inlet velocity may be permissibly high.

As part of this invention, the stator blades may somewhat protrude into the impeller casing to an even closer proximity to the central part of the impeller blades and may somewhat conform to the blades, to further improve efficiency. This is shown in this Figure.

The inlet is shown to be of uniform diameter, but it may also have a forward enlargement rearward reduction around the stator. This enlarges the intake opening and tends to improve efficiency.

In the text and claims, by forward enlargement rearward reduction is also meant forward increase rearward decrease of volume over the identical area.

In the centrifugal compressor of FIG. 2, the numeral 1 again indicates an impeller casing, 2 indicates an impeller, and 3 indicates a shaft or spindle carrying the impeller. Outside the periphery of the impeller blade system is a series of diffusing passages 9 of any suitable form or distribution, but any other diffusing means may be used. The numeral 5 indicates an air inlet to the central part of the impeller, and the inlet 5 is provided with a stator 6, with its blades slanted against the impeller in the general direction of rotation. A rotor ill is disposed in front of the stator 6, and the rotor and stator are disposed so that the entering fluid must pass through their blades before entering the impeller. The rotor 10 and the stator 6 form a stage. The rotor will produce velocity, and the stator will reduce velocity with increase of pressure. The inlet 5 has a forward enlargement rearward reduction around the rotor-stator stage. The forward enlargement increases the size of the intake opening, and the rearward reduction is instrumental in precompressing the fluid in the inlet before it enters the impeller. The slanted blades of the stator 6 will also direct the precompressed fluid flow against the impeller blades in the general direction of rotation.

The speed of the rotor 10 may be pennissibly high, and the rotor may be rotated at a higher speed than the impeller 2. To this end, the rotor 10 is mounted on a sleeve 11 that is free to rotate relating to theimpeller shaft 3. In this particular construction, the sleeve 1 1 is driven from the impeller shaft 3 by an ordinary compound train of gears disposed in the gear box or casing 12. This is an expansion gear so that the rotor 1t] revolves at a higher speed than the impeller 2, perhaps twice as fast. Gearing is well known and is not shown in detail. The extra high speed of the intake rotor will increase the mass of intake and intake velocity.

Any other means may be used to rotate the rotor 10 at a higher speed than that of the impeller 2.

FIG. 3 is similar to FIG. 2, but an extra stator 6 is disposed in front of the rotor 10. This front stator will direct the intake fluid against the rotor 10 in the general direction of rotation.

A front stator in the inlet will improve efficiency, especially at high speed.

FIG. 4 shows a compressor with plural rotor-stator stages in the inlet conduit. The numeral 1 indicates an impeller casing, 2 indicates an impeller, 3 indicates a shaft or spindle, and 5 indicates an inlet conduit. The numeral indicates rotors, and the numeral 6 indicates stators, the rotors and stators forming stages. The rotors will produce velocity energy, and the stators will reduce velocity energy with increase of pressure energy. The inlet 5 has a forward enlargement rearward reduction around the rotor-stator stages. The forward enlargement increases the size of the intake opening, and the rearward reduction is instrumental in precompressing the fluid in the inlet conduit before it enters the impeller. The slanted blades of the last stator will also direct the precompressed fluid flow against the central impeller blading in the general direction of rotation.

The last stator, directly in front of the impeller, may be omitted; then the last stator is a set of guide vanes.

In this FIG. 4, I substantially increase the size of the intake opening, and I effectively precompress the fluid in the inlet before it enters the impeller.

In FIG. 5, the numeral 1 again indicates an impeller casing, 2 indicates the impeller, 3 the shaft, and 5 the inlet conduit. The numeral 13 indicates guide vanes mounted on the impeller or contiguous thereto and rotating as one with the impeller, and the numeral 6 indicates a stator in front of the guide vanes 13. The stator blades are slanted so as to direct the fluid against the guide vanes in the general direction of rotation. The inlet is shown to be of uniform diameter, but it also may have a forward enlargement rearward reduction around the stator and/or guide vanes.

With the stator 6, the size of the intake opening may be permissibly large, and the inlet velocity may be permissibly high.

A rotor may be disposed in front of the stator 6, and there also may be plural rotor-stator stages in the inlet, as shown in some of the other Figures.

In FIG. 6, the numeral 1 indicates the impeller casing, 2 the impeller, 3 the main shaft carrying the impeller, 5 an inlet conduit of forwardly expanded rearwardly reduced volume, 13 indicates guide vanes mounted on the impeller or contiguous thereto and rotating as one with the impeller, and the numeral 14 indicates separate guide vanes. The separate guide vanes are rotated at a higher rate of speed than that of the impeller. To that end, the numeral 11 indicates a sleeve rotating at a higher speed than the impeller, and the separate guide vanes 14 are mounted on the sleeve. The high speed gearing may be similar to that suggested in FIG. 2, but any other suitable arrangement may be used. The extra high speed of the separate guide vanes will increase the mass of intake and intake velocity.

Separate guide vanes, revolving faster than the impeller, may also be disposed directly in front of the central part of the impeller, if there are no impellermounted guide vanes. In the centrifugal compressor of FIG. 7, the numeral 1 indicates the impeller casing, 2 indicates the impeller, 3 the shaft, 5 the inlet, and 10indicates a single or first rotor. The numeral 15 indicates a peripheral aperture in the inlet casing radially outward of the rotor. During operation, air will be drawn through the peripheral aperture to the blade tips of the rotor, thereby increasing the mass of intake.

The rotor 10 may be a set of separate guide vanes as shown, or may comprise impeller-mounted guide vanes, or may be the rotor of a first stage. The peripheral aperture 15 may be of any shape or form. To obtain greatest suction efficiency, the aperture extends forwardly beyond the leading edges of the rotor blades and rearwardly no further than the trailing edges of the blades, as shown. However, the aperture may have any suitable width and may be narrower or wider than the blade chords, or have the same width.

This peripheral aperture feature may be applied to any centrifugal compressor, blower or pump having a rotor or guide vanes besides the impeller proper.

In the centrifugal compressor of FIG. 8, the numeral 1 again indicates the impeller casing, 2 the impeller, 3 the shaft, 5 the inlet, and 10 a rotor. The rotor may comprise separate guide vanes as shown, or may comprise impeller-mounted guide vanes, or may be the rotor of a first stage.

The rotor 10 is projected from the lip of the inlet casing. During operation, peripheral air is drawn to the blade tips of the projected rotor and is moved into the inlet, thereby increasing the mass of intake.

The projected rotor will also reduce the tendency of air breakaway from the lip of the inlet conduit, which may occur under relatively low forward speed conditions if the lip is disposed forwardly of the leading edges of the first rotor.

This projection feature may be applied to any centrifugal compressor, blower or pump having a rotor or guide vanes besides the impeller proper.

The invention may be used in compressive and noncompressive centrifugal devices, that is, in compressors, blowers and pumps. The devices may or may not have a diffuser outward of the periphery of the impeller, depending on the type and nature of the devices and depending on choice. In non-compressive devices, the numerals 4 and 9 may merely indicate outlets.

The invention may also be adapted to immediate propulsive purposes. In this case, the pressure head delivered centrifugally is converted into velocity in an axial direction, and suitable velocity nozzles or diffuser nozzles may be arranged at the outlet to direct and/or diffuse the flow as desired.

The stator blades in the inlet may be adjustable or variable. Blade adjustment and variability are well known in the art and are not illustrated.

The improvements illustrated in the different Figures and described are interchangeable, and they may be used singly or in any combination.

It is also to be noted that changes may be made without departing from the spirit or scope of the invention I claim:

LII 

1. In a device of the class described wherein an impeller is mounted on a shaft in a casing and is revolved, wherein fluid enters the impeller near the shaft and experiences an outward flow due to centrifugal action, and wherein a rotor-stator stage is disposed upstream of the impeller so that the stator of the stage is interposed between the rotor of the stage and the impeller, the improvement comprising: means revolving the rotor of sAid rotor-stator stage faster than the impeller. 